Pneumatic relay

ABSTRACT

An adjustable gain pilot relay incorporates a body member having a pair of axially aligned valve seats therein and a valve plug coacting with each valve seat and supported by flexures which center the valve plugs relative to the valve seats and which hold the valve plugs in their operating positions. The valve plugs are adjustable relative to one another and to the valve seats in a novel manner such that both ports may be open at a steady-state condition, both valve ports may be closed at a steady-plate condition, or that some travel of the exhaust valve stem relative to the relay housing is necessary to open either valve port. Thereby adjustment of the relay gain is made.

United States Patent Buls et a1.

1541 PNEUMATIC RELAY [72] Inventors: Melvin Lawrence Buls; Gerald FrankVarnum, both of Marshalltown, Iowa [73] Assignee: Fisher ControlsCompany, Inc. [22] Filed: Feb. 9, 1970 [2]] Appl. No.: 9,853

Cooksley ..137/625.27 Bowditch 137/82 Primary Examiner-Alan CohanAttorney-Molinare, Allegretti, N-ewitt & Witcolf 57 ABSTRACT Anadjustable gain pilot relay incorporates a body member having a pair ofaxially aligned valve seats therein and a valve plug coacting with eachvalve seat and supported by flexures which center the valve plugsrelative to the valve seats and which hold the valve plugs in theiroperating positions. The valve plugs are adjustable relative to oneanother and to the valve seats in a novel manner such that both portsmay be open at a steady-state condition, both valve ports may be closedat a steady-p1ate condition, or that some travel of the exhaust valvestem relative to the relay housing is necessary to open either valveport. Thereby adjustment of the relay gain is made.

6 Claims, 8 Drawing Figures [52] US. Cl ..l37/596.l8, 137/84 [51] Int.Cl. ..Fl5b 9/03, FlSb 9/08 [58] Field of Search.....137/82, 84, 596.18,596, 102, 137/625.27

[56] References Cited UNITED STATES PATENTS 2,919,711 1/1960 Lord..137/627.5 X 3,548,879 12/1970 Wilde ..137/627.5 X 1,887,322 11/1932Nettleton ..137/82 PATENTED 19 3.692 054 l PNEUMATIC RELAY BACKGROUND OFTHE INVENTION This invention relates to a pilot relay and moreparticularly, to an improved pilot relay having novel flexure supportsfor each of the valve plugs therein and means for readily adjusting thepositions of the valve plugs within the pilot relay relative to oneanother and to their valve seats.

In one important application, the new and improved pilot relay of thisinvention is used as the power amplifier in a positioner mechanism whichcontrols the position of an actuator. An input signal to the positionercreates a pressure condition to the input section of the relay resultingin a change in pressure to the actuator. The actuator motion istransferred by a series of levers and springs which provides a feedbackforce to the input element of the positioner which balances the newinput force.

A pilot relay of a type to which the present invention generally relatesis provided with a housing having a supply inlet, an exhaust outlet, anoutlet opening communicating with the actuator, and a signal openingcommunicating with an electro-pneumatic valve positioner, as forexample, a torque motor beam which is responsive to an electrical signalfor regulating the output from a nozzle. Valve plug means are reciprocalin the cavity or chamber of the valve housing. Ordinarily,

- a standard double poppet valve is employed, with a diaphragm or likemeans being used to adjust the poppet valve so as to selectivelyposition the valve elements between (I) a first position wherein theinlet is closed and the outlet is open, (2) a second position whereinthe outlet is closed and the inlet is open and (3) an intermediate orsteady-state position wherein both the inlet and the outlet are open forventing the supply pressure to atmosphere so as to maintain the requiredpressure necessary to position the stern in the actuator. A limitationof the standard double poppet valve is that it usually comprises asingle piece carrying lands which contact the inlet and outlet valveseats, with no means for adjusting the position of the two plugsrelative to one another.

The prior art has suggested separating a pair of cooperating valveswithin a relay or a valve member so as to make them separately operableone with respect to the other in the control of axially aligned valveseats. Boyer US. Pat. No. 2,919,7l6for example, discloses a valvemechanism having a pair of aligned valves, each of which engages a valveseat, the valves being in part actuated by an intermediate memberseparate from each.

It is also old to provide a pair of axially aligned members, oneslidable upon the other to control passage of fluid through a pair ofaligned openings. A device incorporating such aligned valves is shown inGreenlees US. Pat. No. 3,004,526.

Yet another form of mounting a pair of aligned valves so as to renderthem movable one with respect to the other along a common axis is shownin Lindquist US. Pat. No. 3,195,416, 195, wherein a pair of valves areseparately resiliently mounted on a stem for movement toward and awayfrom aligned valve seats. These prior arrangements do not include meansfor readily adjusting the positions of the valves relative to oneanother and to their valve seats.

An object of the present invention is to provide an improved pilot relaywhich incorporates a pair of aligned valve plugs movable toward and awayfrom a pair of aligned seats, with novel flexure means being provided tosupport the valve plugs within the valve housing.

Another object of the present invention is to provide an improved pilotrelay wherein the location of the valve plugs with respect to oneanother and to their valve seats may be adjusted in a simple mannerthereby creating a new relay gain or ratio of input signal pressure tooutput pressure.

Still another object of this invention is to provide an improved pilotrelay wherein a pair of aligned valve plugs are flexure mounted, andwherein the supply valve stem is adjustable so as to permit valve travelto be more precise than would be economically possible if reliance werehad on dimensional tolerances alone.

Yet another object of this invention is to provide an improved pilotrelay which is economical to manufacture and reliable in use. Otherobjects and advantages of the present invention will become moreapparent hereinafter.

BRIEF DESCRIPTION OF THE DRAWING ing the operation of the pair of valveplugs with respect to their respective valve seats in differentoperatingphases.

DETAILED DESCRIPTION OF THE PRESENT INVENTION In FIG. 1 there isillustrated schematicallya system incorporatingthe pilot relay of thepresent invention. Provided in the system is an actuator 10 whichincludes a housing having therein a pressure responsive element 12 as,for example, a diaphragm, which is adapted to be connected to anactuating stem or rod for positioning a valve in a conduit (not shown)to regulate fluid flow therethrough. A spring 16 disposed concentricallyabout the rod 14 acts against the diaphragm 12 in opposition to thepressure in the chamber above the diaphragm.

Also provided in the system is a valve positioner 20 of theelectropneumatic type. Positioner 20 comprises a torque motor 22 havingan armature 24 which is adapted to be positioned so as to control thebleed of fluid pressure from a nozzle opening 26. The torque motor 22responds to a direct current milliampere input signal and causes thearmature 24 to pivot about axis 21. Feedback means 27, which will bemore fully described hereinafter, are operative between the actuatingstem 14 of the actuator 10 and the armature 24 of the torque motor 22.

The pilot relay 30 (FIGS. 1 and 2) of the present invention comprises ahousing 32 which has a supply inlet opening 34 therein connected to asupply conduit 36 that is in turn communicated with a source of supplypressure. Disposed within housing 32 is a cavity or chamber 38 whichcommunicates with the supply inlet opening 34 by means of an internalpassageway 40 in housing 32.

A seat ring assembly 42, which has defined thereon a pair of valve seats44 and 46, is located in cavity or chamber 38. O-rings are provided toseal between the seat ring assembly 42 and the walls of chamber 38.Valve members or valve plugs 43 and 45 are adapted to cooperate with thevalve seats or ports 44 and 46. Each of the valve members 43, 45 isretained in an operating position and centered with respect to the ports44 and 46 by flexure members or flexures 48 and 50, respectively. Eachof the valve plugs 43 and 45 is secured, such as by spot welding, toflexures 48 and 50, respectively. Then with the valve plugs 43 and 45centered in the valve seats 44 and 46, respectively, each of theflexures 48 and 50 is secured, such as by spot welding, to the seat ringassembly 42. As will be more fully explained later, the supply valvestem 52 is threadedly engaged with the supply valve member 45 and isadapted to extend through a central passage in the seat ring assembly 42and abut the end of the exhaust valve stem 54 extending through theexhaust valve member 43. The valve member 43 is slidable with respect tothe exhaust valve stem 54 and is biased against the shoulder of theexhaust valve stem 54, as viewed in FIG. 1, by means of the spring 56.

The seat ring assembly 42 is maintained in place by corrugated springwasher 53 which acts between the cover 31 which is affixed to and formsa part of housing 32 and special washer 51, which may be made from analuminum alloy.

Also provided in the cavity or chamber 38 within the housing 32 is adiaphragm or pressure responsive member 60. The pressure responsivemember 60 is biased upwardly, as viewed in FIG. 1, by the resilientmeans or spring 61 which acts against the pressure in the chamber 62defined between the top of the diaphragm 60 and the interior wall of thehousing 32.

Also provided in the cavity or chamber 38 within the housing 32 is adiaphragm or pressure responsive member 60. The pressure responsivemember 60 is biased upwardly, as viewed in FIG. 1, by the resilientmeans or spring 61 which acts against the pressure in the chamber 62defined between the top of the diaphragm 60 and the interior wall of thehousing 32.

A nozzle restriction and adaptor assembly 70 is provided in the housingmember 32 within passage 40 for reducing the supply pressure supplied tothe nozzle passage 77 from supply conduit 36. An O-ring seal is disposedabout the assembly 70 to seat between the assembly 70 and housing 32 andprevent communication between passages 40 and 77 except through assembly70. Conduit 72 communicates with supply inlet opening 34 through aninternal passage in assembly 70 and signal opening 77. The chamber 62above the diaphragm 60 communicates with the nozzle 26 of the torquemotor assembly 22 via signal'opening 77 and conduit 72. Further, outputchamber 41 within seat ring assembly 42 connects to actuator through apassage 73 in the housing 32, the outlet opening 74 and a conduit 75that communicates outlet opening 74 with the chamber 13 above thediaphragm 12 in actuator 10.

One feature of this invention is the construction of the flexures 48 and50. Reference will now be made to flexure 48 shown in FIG. 3, however,it should be understood that the comments likewise apply to flexure 50,since the flexures 48 and 50 are identical. Flexure 48 comprises a thindisc-like member made from metal, for example, spring tempered stainlesssteel and being cut out with generally Y-shaped recesses 80, 81 and 82which provide intermediate supports 84, 85, and 86 for the centralportion 88. The thickness of the flexure 48 is on the order of00045-00055 inch. The central position 88 has an opening 89 forreceiving and holding a valve plug. The central portion 88 can move orflex axially relative to the outer ring-like portion, yet it will notrotate about the axis of the flexure. Thus, a valve plug held in thecentral portion 88 of the flexure 48 such as by spot welding can becentered with respect to its associated valve seat. Further, the flexure48 can be retained within the pilot relay 30 such that it will tend tomaintain the valve plug 43 carried thereon in a desired position, forexample, an operating position.

Considering now the overall functioning of the system, it is to be notedthat an increase in the DC milliampere signal to the coils of the torquemotor 22 causes the armature 24 to rotate about pivot 21, covering thenozzle 26. The resulting flow restriction of nozzle 26 produces anincreased pressure in the nozzle chamber, in conduit 72, and in theupper chamber 62 of the relay 30. For large input signals, the increasednozzle pressure on the relay diaphragm 60 moves the relay exhaust valvestem 54 downward, closing the exhaust port or valve seat 44 and openingthe supply port or valve seat 46. Supply air flows from the conduit 36through passage 40, open port 46, output chamber 41, passage 73 andconduit 75, to increase the output pressure to the chamber 13 above thediaphragm 12 in the actuator 10, moving the actuating stem or actuatorrod 14 downward, as viewed in FIG. 1.

For small input signals, the increased nozzle pressure on the relaydiaphragm 60, forces the exhaust valve stem 54 downward, moving theexhaust valve plug 43 toward the exhaust valve seat 44 and moving thesupply valve plug 45 away from the supply valve seat 46. The resultingthrottling action permits a larger volume of fluid, for example, air toflow into the output chamber 41 through the supply port 46 than from theoutput chamber 41 through the exhaust port 44. This increases the outputpressure to the chamber 13 above the diaphragm 12 and forces theactuating stem 14 to move downward.

The movement of actuating stem 14 is fed back to the armature 24 of thetorque motor 22 by a mechanical linkage means 27 which includes links27a, 27b, 27c and 27d. Link 27a is fixedly secured at one end to theactuating rod 14. The free end of link 27a is pivoted on link 27b. Link27b pivots at the other end on link 270 which is pivoted on a support.Link 270 cooperates with link 27d which is pivoted on a support. Afeedback spring 28 acts between the other end of link 27d and armature24. The resultant feedback motion causes the armature 24 to rotate awayfrom the nozzle 26. Nozzle pressure at nozzle opening 26 decreases,reducing the pressure in the chamber 62 and thereby reducing thedownward force on the exhaust valve stem 54. The spring 61 will bias thediaphragm 60 upwardly and permit the lower flexure 50 to move the supplyvalve plug 45 toward the supply valve seat 46 and the upper flexure 48to move the exhaust valve plug 43 away from the exhaust valve seat 44,causing the flow through both ports 44 and 46 to be equal and preventingany further increase in output pressure. The actuator is once again atsteady-state, but at a higher input signal and a new actuating stem 14position.

When the DC input signal to the torque motor 22 decreases, the armature24 rotates to uncover the nozzle 26, decreasing the pressure in thenozzle chamber and the relay chamber 62. The relay diaphragm 60 movesupward reducing the downward force on the exhaust valve stem 54. Forlarge input signals this permits the lower flexure 50 to close thesupply port 46 and the upper flexure 48 to open the exhaust port 44. Airbleeding through the exhaust port 44 passes through outlet 69 intoexhaust conduit 71 to the atmosphere and decreases the output pressureto the diaphragm 12 in the actuator 10. This permits the actuator stem14 to travel upward so as to suitably position the control deviceconnected thereto. a

For small input signals, the reduced downward force on the exhaust valvestem 54 permits the lower flexure 50 to move the supply valve plug 45toward the supply valve seat 46 and the upper flexure 48 to move theexhaust valve plug 43 away from the exhaust valve seat 44. The resultingthrottling action allows a larger volume of air to flow from the outputchamber 41 through the exhaust port 44 than into the output chamber 41through the supply port 46. This decreases the output pressure to theactuator diaphragm 12 in the actuator 10 and permits the actuator stem14 to move upward. Actuating stem .14 movement is fed back to thearmature 24 by the mechanical linkage 27 to reposition the armature 24.The exhaust valve plug 43 moves toward the exhaust valve seat 44 and thesupply valve plug 45 moves away from the supply valve seat 46,establishing equal flow rates through both ports. This prevents anyfurther decrease in output pressure and results in steady-stateconditions.

With reference to FIGS. 4a, 4b, 4c, 4d, and 4e, there is illustrated thevarious positions of the valve plugs 43 and 45 during operation of therelay 30. In FIG. 4a, the supply valve plug 45 is closed, the exhaustvalve plug 43 is fully open, and there is maximum exhaust of pressure tothe atmosphere through opening 69. In FIG. 4b,

the supply valve plug 45 is just closed and the exhaust valve plug 43 isopen somewhat so as to permit some exhaust. FIG. 4c illustrates anintermediate position wherein both the supply valve plug 45 and theexhaust valve plug 43 are open. FIG. 4d illustrates the exhaust valveplug 43 just closed and the supply valve plug 45 open somewhat and FIG.4e illustrates the position of maximum supply with the supply valve plug45 fully open and the exhaust valve plug 43 closed.

Another feature of this invention is the means for adjusting theeffective length of the supply valve stem 52, so as to adjust theposition of the valve plugs 43 and 45 relative to one another and totheir valve seats to accommodate manufacturing tolerance considerationsas well as to provide for adjustment of the valve plug positions therebychanging the operating gain of the relay 30. The flexures 48 and 50 aresecured to the valve plugs 43 and 45 so as to retain same in a centeredrelationship with respect to the valve seats 44 and 46, respectively. Inaddition, the flexures 48 and 50 serve as springs to bias the valveplugs vertically upward toward their operating positions. Anotherfunction is served by the flexure 50, namely, to provide an antirotationmeans so as to hold the valve plug 45 and enable rotation of the valvestem 52 relative to the valve plug to which it is threadedly secured. Bychanging the effective length of the supply valve stem 52, that is, thedistance between the valve plugs 43 and 45 and their relationship to thevalve ports, a much more precise relay gain is permitted than would beeconomically possible if reliance were based on dimensional tolerancesalone. The effective length of the valve stem 52 can be changed suchthat both ports 44 and 46 may be open at a steady-state condition, bothports may be closed at a steadystate condition, or that some travel ofthe exhaust valve stem 54 relative to the relay housing 32 is necessaryto open either valve port. Thereby adjustment of the relay gain is made.Inthe application shown, the valve stem 52 is adjusted such that bothports are open at a steady-state condition. The resulting continuousbleed determines the sensitivity of the relay 30 for small variationsabout the steady state condition.

There has been provided by the: present invention an improved adjustablegainpneumatic pilot relay which produces improved performance in asystem as shown, for example, in FIG. 1 of the application. Incorporatedwithin the improved pneumatic relay or power amplifier are a pair ofvalve plugs which are flexure mounted so as to maintain the alignment ofthe valve plugs with their respective valve seats and to hold the valveplugs in their operating positions. The supply valve stem is adjustablyconnected to the supply valve plug so as to enable adjustment of theeffective length of the supply valve stem and, therefore, the distancebetween the two valve plugs. A simplified arrangement is thereby prosaryto open either valve port. Thereby adjustment of the relay gain is made.

While a presently preferred embodiment of the invention has been shownand described, it is apparent that various changes and modifications maybe made therein without departing from the invention. Therefore, it isintended in the appended claims to cover all such changes andmodifications as fall within the true spirit and scope of the invention.

We claim:

1. A pilot relay comprising a housing having a cavity therein, meansdefining a pair of valve seats, means defining a supply inlet into saidcavity and adapted to communicate with a source of supply fluidpressure, means defining an exhaust outlet from said cavity and adaptedto be vented to the atmosphere, means defining an outlet passage fromsaid cavity, means defining a signal passage from said cavity, saidvalve seats being aligned with one another, the first valve seat beingdisposed between the supply inlet and the outlet passage, the secondvalve seat being disposed between the outlet passage and the exhaustoutlet, first and second valve means disposed in the cavity forselectively opening and closing the valve seats, flexures supporting thefirst and second valve means and centering them with respect to thevalve seats, pressure responsive means operatively connected to thesecond valve means, each valve means comprising a valve plug and a stem,the first stem abutting the second stem, the second valve plug beingslidable on the second stem, the first stem being adjustably secured tothe first valve plug to permit adjustment of the first valve plugrelative to the second valve plug, whereby the valve plugs are movableaxially relative to one another and each valve plug can continue to openfurther after the other valve plug is seated.

2. A pilot relay as in claim 1, wherein said first valve means flexurenon-rotatably supports the first valve plug and the first stem isthreadedly supported in the first valve plug such that rotation of firststem relative to the first valve plug will change the effective lengthof first stem between the first valve plug and the second valve plug.

3. A pilot relay as in claim 1, wherein a seat ring assembly is disposedin said cavity, the valve seats being on the seat ring assembly.

4. A pilot relay as in claim 1, wherein the first valve means flexureand the second valve means flexure function to retain the first valvemeans and second valve means in their operating positions.

5. A pilot relay as in claim 4, wherein the flexures each comprise aflat disc-like member having an outer peripheral portion and a centralportion connected to the peripheral portion by spaced intermediatesupports, the central portion having an opening for receiving a valvemeans therein.

6. A pilot relay as in claim 5, wherein a first valve means flexure issecured to the central portion of said first valve plug and a secondvalve means flexure is secured to the central portion of the secondvalve plug.

1. A pilot relay comprising a housing having a cavity therein, meansdefining a pair of valve seats, means defining a supply inlet into saidcavity and adapted to communicate with a source of supply fluidpressure, means defining an exhaust outlet from said cavity and adaptedto be vented to the atmosphere, means defining an outlet passage fromsaid cavity, means defining a signal passage from said cavity, saidvalve seats being aligned with one another, the first valve seat beingdisposed between the supply inlet and the outlet passage, the secondvalve seat being disposed between the outlet passage and the exhaustoutlet, first and second valve means disposed in the cavity forselectively opening and closing the valve seats, flexures supporting thefirst and second valve means and centering them with respect to thevalve seats, pressure responsive means operatively connected to thesecond valve means, each valve means comprising a valve plug and a stem,the first stem abutting the second stem, the second valve plug beingslidable on the second stem, the first stem being adjustably secured tothe first valve plug to permit adjustment of the first valve plugrelative to the second valve plug, whereby the valve plugs are movableaxially relative to one another and each valve plug can continue to openfurther after the other valve plug is seated.
 2. A pilot relay as inclaim 1, wherein said first valve means flexure non-rotatably supportsthe first valve plug and the first stem is threadedly supported in thefirst valve plug such that rotation of first stem relative to the firstvalve plug will change the effective length of first stem between thefirst valve plug and the second valve plug.
 3. A pilot relay as in claim1, wherein a seat ring assembly is disposed in said cavity, the valveseats being on the seat ring assembly.
 4. A pilot relay as in claim 1,wherein the first valve means flexure and the second valve means flexurefunction to retain the first valve means and second valve means in theiroperating positions.
 5. A pilot relay as in claim 4, wherein theflexures each comprise a flat disc-like member having an outerperipheral portion and a central portion connected to the peripheralportion by spaced intermediate supports, the central portion having anopening for receiving a valve means therein.
 6. A pilot relay as inclaim 5, wherein a first valve means flexure is secured to the centralportion of said first valve plug and a second valve means flexure issecured to the central portion of the second valve plug.